1. Field
The invention relates to a process useful to produce vitamin D analogs, such as calcitriol, sold under the brand name Rocaltrol.RTM..
2. Description
Processes for manufacturing vitamin D analogs typically require multiple steps and chromatographic purification. See, Norman, A. W.; Okamura, W. H. PCT Int. Appl. WO 9916452 A1 990408; Chem Abstr. 130:282223. Batcho, A. D.; Bryce, G. F.; Hennessy, B. M.; lacobelli, J. A.; Uskokovic, M. R. Eur. Pat. Appl. EP 808833, 1997; Chem. Abstr. 128:48406. Nestor, J. J.; Manchand, P. S.; Uskokovic, M. R. Vickery, B. H. US 5872113, 1997; Chem. Abstr. 130:168545. The present invention seeks to provide an efficient synthesis of the A-ring portion of such vitamin D analogs.